It is common practice to estimate the standard (E⁰) or formal (E⁰’) potential from cyclic voltammetric data. A frequent estimate of E⁰ or E⁰’ is taken from either the peak potential (E_p), the half wave potential (E_1/2), or the average of the cathodic and anodic peak potentials (E_pc+E_pa)/2. Often, this suffices to identify the standard or formal potential within 100 mV, but confidence in such estimates is not always justified. Mechanisms that include both electron transfer (E) and chemical (C) steps can impact the quality of estimated standard and formal potentials. In some systems, limitations to the estimated standard and formal potentials depend on the rates of heterogeneous electron transfer and homogenous reactions.

Here, the quality of estimated standard and formal potentials based on peak potentials, half-wave potentials, and average potentials for the cathodic and anodic sweeps are described for various mechanisms. Cases where the standard and formal potentials are well estimated from measured cyclic voltammetric data are identified and the quality of the estimated standard and formal potentials are characterized. That is, specify whether the estimate is within 100 mV, 50 mV, or 10 mV for a given mechanism. Situations where the estimate fails are identified and alternative means to estimate the standard and formal potential are provided. Several reaction schemes that include EC, EE, CE, and the various ECE mechanisms are characterized.